H alpha question / puzzle

Here is a question for you H alpha men out there.

If you look at many published solar H alpha images, you see the character of the disc as a series of swirly lines.

Here is a typical example from Daytstar’s web-site:


If you look at the GONG images, you never see any character like this. I tend to regard GONG images as definitive as they have a band-width of 0.4 Angstroms centred at 6562.8 Angstroms. The GONG images are usually “mottled”, but never have the general swirls as in the image above. It looks nice, but where does the swirly stuff come from?

I have never seen this kind of character, and in fact my images such as the most recent one I posted: (https://roslistonastronomy.uk/window-sill-back-in-action) tend to be similar to the GONG ones. In fact, the only time I got anything like the swirls was when autostakkert was playing up!

Anyone any ideas?

2 Responses

  1. I would have thought that if there is enough light, a single shot would in fact be better for detail. The usual reason for stacking is to reduce instrument noise at the cost of blurring due to turbulence as the details shift across multiple exposures. There isn’t much evidence of noise on the GONG images. Before my old Canon camera broke, I used to get better detail on white-light images of the granulation with a single frame than I now do stacking frames from the Mikrokular or PD.

  2. Hi Roger,

    Is it that the Gong images are single snapshots, so the “mottling “effect is the lack detail, blurring due to atmospherics, whereas H alpha pictures taken with quark, lunt, etc are stacks of multiple images, with manipulation of the wavelets to bring out the detail, which will also depend upon the “seeing”, chip /pixel size etc.

    Pete H

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